As I was digging through the articles I've collected to read and post about, I came across this one with some research conducted by some local mental health professionals, amongst others. The study described in the article was a large multi-site data analysis in which adolescents with a Major Depressive Episode were followed-up over the course of several years after treatment. The researchers found that:

recovery rates were good, with 96.4% of participants recovering during the follow-up period, with over two-thirds recovering during the first year of treatment.
treatment modality was unrelated to recovery.[1]
nearly half of those who recovered had a recurrence of symptoms within 5 years.

We've long known that a past major depressive episode predicts a future one. As a result, this finding is not surprising. What is interesting about the research here is that there is a predictive factor of both gender and co-occuring anxiety disorder.

As far as clinical implications go, this finding highlights the importance of skills acquistion for self-recovery after the completion of therapy by a trained professional. In addition, the should focus not just on the management of the depression symptoms but also of the anxiety features present. I'd like to see more follow-up on specific types of therapy and the longevity of their effects, but longitudinal study is hard and expensive, so we may never get to see that clinical application of these findings.

Depression isn't forever, but like an unwelcome houseguest, it finds its way back. Be ready.

Footnotes: [1] This was not a study looking at the efficacy of various types of treatment, just a look at the efficacy of all treatments. The treatment options for participants in this study received either Cognitive Behavioral Therapy, fluoxetine (prozac), a combination or a placebo.